[rofrol]

>The difference between fastest and slowest is only 43ms (0.043 seconds), and I saw around this difference between rendering the same css twice. I think it is best to go for whatever is most readable for you. Personally I find :first-child the most understandable at a glance.

https://www.reddit.com/r/web_design/comments/5u6e7b/comment/...

[majou]

43ms is quite a slowdown isn't it? Handful of joules at least.

[jraph]

Actually, the only two comparable / equivalent options exposed in this page related to this discussion, ul > * + * vs li:not(:first-child), are 50.8ms vs 40.9ms (respectively) for 10 page loads. The browser is not named, so I would guess Chrome. I'm not convinced the difference is not proven significant, we need more data points than that to know for sure, but it seems insignificant. So yes, readability should be the determining factor here.

Other browsers might see different results, especially Firefox which has a very fast / efficient CSS engine.

ps: a difference of 43 ms for one page load would be huge indeed. By comparison, a frame in a 30 fps video is 33 ms.